Cyclopropane monoacetal derivatives represented by the below-mentioned formula (III) (hereinafter sometimes to be abbreviated as cyclopropane monoacetal derivative (III)), for example, 1-(dialkoxymethyl)cyclopropanecarbaldehyde represented by the formula (IV) as a known compound
are useful as raw material for antibacterial agents. A compound represented by the formula (IV) is synthesized, for example, by monoacetalization of a dicarbonyl compound corresponding to said compound in the presence of an acid catalyst and using an ortho ester, and led, via several steps, to amino-substituted azaspiroalkane which is an intermediate for synthetic antibacterial agents (see WO02/14278). However, this method is associated with problems of inability to avoid contamination with a remaining dicarbonyl compound, which is a starting material, a diacetal compound produced by an over reaction, and the like.